1. Field of the Invention
The present invention relates to minimally invasive spinal stabilization systems, more particularly to a new and improved inner and outer sleeve assembly used to simplify and expedite minimally invasive spinal stabilization surgery.
2. Description of the Prior Art
Bone may be subject to degeneration caused by trauma, disease, and/or aging. Degeneration may destabilize bone and affect surrounding structures. For example, destabilization of a spine may result in alteration of a natural spacing between adjacent vertebrae. Alteration of a natural spacing between adjacent vertebrae may subject nerves that pass between vertebral bodies to pressure. Pressure applied to the nerves may cause pain and/or nerve damage. Maintaining the natural spacing between vertebrae may reduce pressure applied to nerves that pass between vertebral bodies. A spinal stabilization procedure may be used to maintain the natural spacing between vertebrae and promote spinal stability.
Spinal stabilization may involve accessing a portion of the spine through soft tissue. Conventional stabilization systems may require a large incision and/or multiple incisions in the soft tissue to provide access to a portion of the spine to be stabilized. Conventional procedures may result in trauma to the soft tissue, for example, due to muscle stripping.
Spinal stabilization systems for a lumbar region of the spine may be inserted during a spinal stabilization procedure using a posterior spinal approach. Conventional systems and methods for posterolateral spinal fusion may involve dissecting and retracting soft tissue proximate the surgical site. Dissection and retraction of soft tissue may cause trauma to the soft tissue, and extend recovery time. Minimally invasive procedures and systems may reduce recovery time as well as trauma to the soft tissue surrounding a stabilization site.
A spinal stabilization system may be installed in a patient to stabilize a portion of a spine. A spinal stabilization system may be installed using a minimally invasive procedure. An instrumentation kit may provide instruments and spinal stabilization system components necessary for forming a spinal stabilization system in a patient.
U.S. Patent Publication No. 2004/0138662 to Landry et al. (hereinafter “Landry”), describes minimally invasive techniques for spinal stabilization. Landry discloses the attachment of a polyaxial screw or bone fastener assembly to a vertebra during minimally invasive surgery. During surgery, the polyaxial screw of Landry is secured to one end of a slotted sleeve using a pair of smaller screws that extend the length of the sleeve. The smaller securing screws are engaged using a driver inserted at the proximal end of the sleeve to accomplish securing the distal end of the sleeve to the polyaxial screw. This attachment prevents the sleeve from becoming disconnected from the polyaxial screw during surgery. Should the sleeve and polyaxial screw become uncoupled during surgery, it would then become necessary to make large incisions to reach the screw to complete the operation such that the surgery is no longer minimally invasive. When the surgery is complete, the smaller screws are undone, and the sleeve is detached from the polyaxial screw and removed. The Landry device and its use are cumbersome in that Landry requires a separate screw in the sleeve as well as a separate driver for engaging and disengaging this screw. The smaller securing screws used in the Landry device are delicate and prone to breakage. Retrieval of broken securing screws is both time consuming and potentially injurious to the patient.
It is therefore desirable to have a simple apparatus and method for securing the engagement of the polyaxial screw during surgery.